The present invention generally relates to rotary recording medium reproducing apparatuses capable of performing address search, and more particularly to a reproducing apparatus capable of performing search by varying the moving speed of a reproducing element during search in accordance with time address and during search in accordance with chapter address, in an apparatus for reproducing a rotary recording medium recorded with time addresses and chapter addresses.
A new information signal recording and/or reproducing system has been proposed in U.S. Pat. Nos. 4,315,283 and 4,322,836, of which the assignee is the same as that of the present application. According to this proposed system, the recording system forms pits in accordance with an information signal being recorded along a spiral track on a flat rotary recording medium (hereinafter simply referred to as a disc), without forming a groove therein. In the reproducing system, a reproducing stylus traces over along this track to reproduce the recorded information signal in response to variations in electrostatic capacitance.
In this system, since no grooves for guiding the reproducing stylus are provided on the disc, it becomes necessary to record pilot or reference signals on or in the vicinity of a track of a program information signal, on the disc. Upon reproduction, the reference signals are reproduced together with the program information signal. Tracking control is carried out so that the reproducing stylus accurately traces along the track in response to the reproduced reference signals.
By use of this previously proposed system, there is no possibility whatsoever of the reproducing stylus or the disc being damaged since the recording track has no groove. The reproducing stylus can trace the same portion of the track repeatedly many times, whereby a special reproduction such as still, slow-motion, or quick-motion reproduction becomes possible. Moreover, operations such as a random access, high-speed search, and automatic cueing operation in which the reproducing stylus is shifted to a position of a desired recorded program where the reproduction is to be started, can be performed with ease.
In order to perform operations such as the above random access, high-speed search, and automatic cueing operations, signals such as an address signal (hereinafter referred to as a chapter address signal) for indicating the number of the recorded program, and an address signal (hereinafter referred to as a time address signal) for indicating the position within the recorded program in reproducing time from the start of that recorded program or in reproducing time from the start of the first program recorded on the disc, are recorded onto the disc.
When performing search operations such as the above random access, high-speed search, and automatic cueing operations with respect to a disc recorded with such an address signal, the address of the position where the reproducing stylus is reproducing and a desired address which has been set are compared. According to the difference between the two addresses, the reproducing stylus is moved at a high speed in a radial direction of the disc. It is desirable to perform such a search operation within a short period of time. Hence, it is desirable to move the reproducing stylus at a high speed so that the search operation is performed within the short period of time.
In a case where the desired set address is a time address, it is always possible to accurately detect the difference between the address of the position where the reproducing stylus is presently located, and the above set address. Accordingly, it is possible to move the reproducing stylus at a high speed when the above difference between the two addresses is large, and move the reproducing stylus at a low speed when the above difference is small, to accurately move the reproducing stylus to the target address position within a short period of time.
On the other hand, if the desired set address is a chapter address, it is detected that the reproducing stylus is at the chapter of the set address when the reproducing stylus enters within the chapter of the set address after searching the chapter of a number preceding the chapter number of the set address by one. Hence, an operation is performed to return the reproducing stylus by amount the reproducing stylus moved in excess after entering the chapter of the set address, and stop the reproducing stylus at the beginning position of that chapter.
Accordingly, if the moving speed of the reproducing stylus is set to a high speed desirable during the time address search, the amount the reproducing stylus moves in excess after entering the chapter of the desired address during the chapter address search becomes large. Thus, time is required to return the reproducing stylus in a reverse direction by the above amount moved in excess, and as a result, more time will be required to search for the desired address. Especially if the recording time of the chapter of a number preceding the chapter number of the set address by one is short, the reproducing stylus is moved in excess and passes by the chapter number preceding the chapter number of the set address when the reproducing stylus is returned in the reverse to direction in an attempt to move the reproducing stylus by the above amount moved in excess. In this case, the reproducing stylus is then moved in the forward direction in an attempt to move the reproducing stylus to the beginning position of the above desired chapter, but the reproducing stylus is again moved in excess because the distance to be moved is short and the speed with which the reproducing stylus is moved is high. The above operation in which the reproducing stylus is moved in excess is repeatedly performed, that is, a hunting phenomenon is introduced. Therefore, in this kind of a case, considerable time will be required to move and stop the reproducing stylus at the set address position.
On the other hand, in order to prevent the above inconvenient phenomenon from being introduced, the speed with which the reproducing stylus is moved must be selected to a speed slower than that for the time address search, which is suited for the chapter address search. However, if the above moving speed is selected to the slow speed suited for the chapter address search, there is a disadvantage in that more time will be required to perform the time address search.